Generally, in a video signal processing apparatus such as a video camera, a television and the like, there is provided an automatic gain adjusting circuit inside, so that gain of input video signals can be automatically controlled. That is, if the level of the video signals is below that of reference signals, then the signals are output after being amplified. On the other hand, if the level of the video signals exceeds that of the reference signals, the signals are controlled so that the output level can be maintained at an even level in order to prevent distortions occurring during amplification.
However, in the case that the automatic gain adjusting apparatus is out of order, or the gain does not show a proper value, there is the problem that a separate gain adjusting apparatus is required to adjust the gain to the desired level again.